Gas turbine engines typically include a fan section, a compressor section, a combustor section and a turbine section. During operation, air is pressurized in the compressor section and mixed with fuel and burned in the combustor section to generate hot combustion gases. The hot combustion gases are communicated through the turbine section, which extracts energy from the hot combustion gases to power the compressor section and the fan section. One or more sections of the gas turbine engine may include a plurality of vane assemblies having vanes interspersed between rotor or fan assemblies that carry the blades of successive stages of the section.
Some gas turbine engines are designed to propel aircraft at supersonic or near supersonic velocities at various altitudes. The relative velocities of the blades within the fan or compressor sections required to propel aircraft at supersonic or near supersonic velocities may generate shock waves, particularly near the outer radial portions of the blades. When such shock waves are introduced into the surrounding flow field, undesirable efficiency depleting losses within the engine may result.
Contributors to decreased efficiency generally include wall friction, tip clearance vortices, hub-corner roll-up and shock waves. When operating at supersonic speeds, shock wave/boundary layer interactions may induce separation at the outer radial spans of the rotor blades, leading to a relatively large reduction in efficiency. In addition, interaction between tip vortices and the supersonic flow create complicated shock structures between adjacent rotor blades, further reducing efficiency. These shock wave related phenomena may dominate efficiency reduction in supersonic flows by reducing the effective aerodynamic throat area between adjacent blades, thereby limiting the mass flow through the rotor. Reduction of efficiency depleting losses in the supersonic flow region of rotors in the fan and compressor stages, thereby increasing the mass flow through these sections as well as the entire compressor, is desirable. This can be achieved, according to various embodiments of the below disclosure, by controlling the shape of inlet vanes that guide flow into rotors experiencing regions of supersonic flow.